JP4585965B2 - Light-reflective painted metal plate - Google Patents

Description

  The present invention relates to a coated metal plate excellent in light reflectivity, and in particular, when maintaining a high light reflectance stably for a long period of time, for example, when used as a reflector of a liquid crystal panel or a reflector of a lighting fixture In particular, the present invention relates to a coated metal plate excellent in light reflectivity and light resistance that maintains high brightness for a long period of time.

The light-reflective coated metal plate is used as a reflector for lighting fixtures that can obtain high brightness with low power consumption. For example, in Patent Document 1, the light reflectance is increased by forming a resin coating containing titanium oxide (TiO ₂ ) as a white pigment on a metal plate. Further, in Patent Document 2, in addition to titanium oxide, a fluorescent pigment that absorbs light having a wavelength with low visibility (it is difficult to sense brightness with human eyes) and converts the light into light with high visibility and emits light. The reflector for lighting fixtures which can feel brighter by using is disclosed.

  On the other hand, various reflection sheets have been proposed in order to increase the luminance of the liquid crystal display device and obtain a brighter display screen. As this type of reflection sheet, for example, a polyethylene terephthalate (PET) film (such as Patent Document 3) that has been whitened by generating a large number of fine bubbles, or a metal thin film such as Al or Ag on the surface of a polymer film. Laminated layers (Patent Document 4 etc.) are known.

By the way, since the installation position of the reflection sheet in the liquid crystal display device is close to the light source, the reflection sheet is required to have heat resistance. However, since the conventional film material is inferior in heat resistance, research is being made on using a metal plate itself that is easy to process and excellent in heat resistance and durability as a reflector. Further, in Patent Document 3, it has been attempted to further increase the heat dissipation by further laminating a heat dissipation sheet on the reflection sheet. However, since the plastic material itself is inferior in heat dissipation, a metal plate excellent in heat dissipation is used. The significance of using as a base material of a reflective sheet is increasing.
Japanese Patent Laid-Open No. 2001-243819 JP 2003-73624 A JP 2004-101893 A JP 2004-145239 A

  Under the circumstances as described above, the present inventors conducted research by focusing on a reflector combined with a fluorescent pigment as described in Patent Document 2, but the initial reflectance was good. I learned that the reflectance may decrease over time. Therefore, research was repeated to provide a coated metal plate that can maintain high light reflectance stably over the long term, and as a result, the invention described in Japanese Patent Application No. 2004-234792 was developed, and a patent application was filed. I'm done.

  This prior invention is a multi-layered light-reflective coated metal plate containing a white pigment and a binder resin, wherein at least one coating layer contains a fluorescent substance as a reflectance improving component, and the fluorescent substance A coating layer that does not contain a fluorescent substance is formed on the upper side of the coating layer that contains, thereby suppressing the photodegradation of the fluorescent substance, improving the light resistance and improving the light reflectivity. It is.

  That is, the fluorescent material gradually deteriorates and loses the fluorescence characteristics when irradiated with light (especially ultraviolet rays). However, the shorter the wavelength, the greater the energy of the light, and the decomposition of the fluorescent material is accelerated. On the other hand, as the wavelength of light is shorter, the amount of attenuation when passing through the coating film is larger. Therefore, when the coating film becomes thicker, it becomes difficult for energy to reach the deep part, and the fluorescent substance contained in the deep part is difficult to deteriorate.

  Therefore, in the above-mentioned invention of the prior application, light on the coating layer containing the fluorescent substance is formed by forming a coating layer not containing the fluorescent substance as a light attenuating layer on the upper side of the coating layer containing the fluorescent substance. As a result, the amount of energy reached can be reduced, and as a result, the photodegradation of the fluorescent substance can be suppressed and the persistence of the fluorescent color development can be increased.

  However, in order to suppress the photodegradation of the fluorescent material by this method, it is necessary to increase the coating thickness of the uppermost layer, which not only increases the coating cost but also increases the light fastness effect that is obtained. Therefore, further improvement is required when considering practicality.

  The present invention has been made under such circumstances, and the object thereof is to effect the amount of ultraviolet rays reaching the lower fluorescent material-containing layer without increasing the thickness of the upper coating layer. The coating composition that can be reduced and the fluorescent properties can be sustained over a long period of time, and as a result, the coating metal that is excellent in light reflectivity and can maintain the reflectivity over a long period of time. To provide a board.

  The light-reflective coated metal plate according to the present invention that has solved the above-mentioned problems is a light-reflective coating provided with a light-reflective coating film having a structure in which a plurality of light-reflective layers containing a white pigment and a binder resin are laminated. A coated metal plate, wherein at least the outermost layer of the light-reflecting coating film is a layer having a thickness of 5 μm or more that does not contain a fluorescent substance, and a layer containing the fluorescent substance or an upper layer side thereof has a melamine It is characterized by the presence of a cross-linked polyester resin layer.

  In the coated metal plate of the present invention, a preferable thickness of the outermost layer in the light reflective coating film is in the range of 5 to 50 μm, and the polyester resin layer having melamine crosslinking is a layer containing a fluorescent substance. It is desirable to provide it on the surface layer side. The type of white pigment to be contained in the reflective layer is not particularly limited, but titanium oxide is most preferable in consideration of practicality. Moreover, the heat-radiation coating film may be formed in the other side of the surface in which the light reflection coating film is formed.

  In a light-reflective coating film having a multi-layer structure, a polyester resin having a melamine bridge as a binder resin in a layer above the layer containing the fluorescent substance in addition to not containing the fluorescent substance in the outermost layer As a result, the amount of ultraviolet rays reaching the fluorescent substance-containing layer can be greatly reduced. As a result, the lifetime of the fluorescent substance is greatly extended, and the high reflectance is stably exhibited over the long term. A light-reflective painted metal plate can be provided. Moreover, if it is set as the coating-film structure which formed the heat-radiation coating film in the back surface side, heat dissipation will improve with light reflectivity, for example, it can utilize effectively as a reflecting plate etc. of a liquid crystal display device. And the reflective coating metal plate of this invention can be widely utilized for the various members which need to reflect light besides the reflecting plate of a liquid crystal display device.

  The light-reflective coating metal plate of the present invention has a light-reflective coating film having a laminated structure, and the reflective coating film includes a white pigment such as titanium oxide in a binder resin to increase the reflectance. In order to further increase the reflectance, a fluorescent substance is included. In the case of a coating film that does not contain a fluorescent substance, for example, titanium oxide used as a white pigment absorbs light of 430 nm or less, and thus a method of increasing the film thickness generally employed as a means for improving the reflectance of the coating film or sheet However, the reflectance of light of 400 to 430 nm does not increase, and as a result, the total reflectance is inferior to that of the conventional product (fine bubble-containing PET film).

  However, since the fluorescent material has an effect of increasing the reflectance by absorbing ultraviolet light having a wavelength of 400 nm or less and emitting visible light, the combined use of the white pigment and the fluorescent material is effective in increasing the reflectance. It becomes a means. However, when a titanium oxide was used as a white pigment and a resin coating film containing this and a fluorescent material was formed, a light resistance acceleration test was performed using a xenon weather meter, and the reflectance decreased with time. This phenomenon was observed. This is presumably because the fluorescent substance was decomposed by ultraviolet rays, and the action of emitting visible light decreased with time.

  Moreover, even after the fluorescent substance contained in the outermost layer is decomposed by ultraviolet rays, the outermost layer still has a considerable ultraviolet absorbing ability, and it is considered that ultraviolet rays are absorbed by the outermost layer thereafter. As a result, the fluorescent material contained in the lower layer (layer closer to the metal plate) than the outermost layer cannot absorb ultraviolet rays and emit visible light, and the effect of improving the reflectivity is gradually increased. It is thought that it can no longer be expressed. Therefore, when a measure for the decrease in reflectance over time was examined, it was effective that the outermost layer of the light-reflective coating film did not contain a fluorescent substance, as was clarified in the preceding invention. I found out.

  Therefore, in the present invention, utilizing the technical idea of the invention of the prior application, as a first requirement, the outermost layer of the light-reflective coating film is not allowed to contain a fluorescent substance.

  However, in order to suppress a decrease in light resistance only with this method, the outermost layer must be thick, which increases the cost. In addition, the entire light-reflective coating layer becomes thick and the coated metal plate becomes thick, which causes a reduction in the weight and compactness of the final product, and further improvements are required.

  Therefore, as a result of repeated research aimed at further improvement, if a polyester resin having a melamine crosslink is used as a binder resin component contained in the layer including the layer containing a fluorescent substance or a layer above it, It was confirmed that the light resistance was further improved as compared with the case of using a polyester-based resin containing another crosslinking agent. Moreover, as the light resistance is increased, there is a concern that the effect of improving the reflectance of the fluorescent material is impaired, but surprisingly, no significant decrease in the reflectance was observed. The reason for this is unclear, but the wavelength range of ultraviolet light that degrades the fluorescent material is shorter than the wavelength range of ultraviolet light that exhibits the fluorescence of the fluorescent material, and the polyester resin having melamine crosslinks is short. This is thought to be due to the selective absorption of ultraviolet rays in the wavelength range.

  Therefore, the polyester resin having melamine crosslinking may be contained as at least part of the binder resin in the layer containing the fluorescent substance, but more preferably above the layer containing the fluorescent substance. It is preferable to make it contain in the layer located in, and it is more preferable to make it contain in the outermost layer. In addition, the polyester resin having melamine cross-linking exhibits its effect only by being contained in only one of the layers containing the fluorescent substance or the layer above it, but it may be contained in two or more layers. If so, the effect is more effectively exhibited, and as a result, the entire light-reflective coating film having a multilayer laminated structure can be thinned, which is preferable.

  By the way, polyester resins having melamine crosslinking generally have high crosslink density due to self-condensation reaction, so that workability is poor, especially when the coated metal plate is bent when the coating film is thick. There are concerns about cracking. However, this concern can be resolved by forming a coating film using polyester resin as the binder resin using isocyanate or blocked isocyanate as the crosslinking agent on the lower layer side of the layer containing the polyester resin having melamine crosslinking. The

  Therefore, the best mode when applied to applications requiring excellent light resistance and workability is that the outermost layer side is a layer containing a white pigment and a polyester resin binder having melamine crosslinking, and the lower layer side is a white pigment. And a coating composition having a two-layer structure or more in which a layer containing a polyester-based resin binder using a fluorescent substance and isocyanate (or blocked isocyanate) as a crosslinking agent is used.

  Thus, according to the present invention, it is possible to provide a light-reflective coated metal plate that has a much lower decrease in reflectance with time than the prior invention, and that is relatively thin and maintains a high reflectance for a long period of time.

In the present invention, when “reflectance” is referred to without particularly limiting the wavelength, the reflectance is measured with a color difference meter Σ90 manufactured by Nippon Denshoku Industries Co., Ltd. every 20 nm between 400 and 700 nm. Means the total reflectivity (%) obtained in (1). In the following equation, R (λ) represents the reflectance at the wavelength λ.
(Total) Reflectivity = {[R (400) + R (420) + ... R (660) + R (680)] + [R (420) + R (440) + ... R (680) + R (700)]} × 20 ÷ 2 ÷ (700-400)

  In the present invention, the outermost surface layer that is important for improving the light resistance needs to have a thickness of 5 μm or more, and if it is too thin, it will not be possible to satisfactorily prevent photodegradation of the fluorescent substance existing on the lower layer side. However, if this outermost layer that does not contain a fluorescent substance becomes too thick, the effect of improving the reflectance of the fluorescent substance existing on the lower layer side is hardly exhibited despite the use of the melamine-crosslinked polyester-based resin. The thickness is preferably 80 μm or less, more preferably 60 μm or less, and still more preferably 40 μm or less.

  The light-reflective coating film in the light-reflective coating metal plate according to the present invention includes a two-layer type of the outermost layer and a layer containing a fluorescent substance, and the outermost layer—a layer containing a fluorescent substance—a fluorescent substance. Various layer configurations such as a three-layer type with no layers, an outermost layer-a layer containing a fluorescent substance-a layer containing no fluorescent substance-a four-layer type containing a fluorescent substance can be adopted. In this case, it is essential that at least one layer including the fluorescent material or a layer including the fluorescent material contains a polyester resin having a melamine crosslink. Even if the outermost layer is a laminate of two or more layers of different binder resins, if any layer does not contain a fluorescent substance, both layers are combined together. A polyester resin having a melamine crosslink may be contained in one or both of the surface layers.

  The thickness of the light reflective coating film is not particularly limited, but is preferably about 30 to 150 μm including the outermost layer.

  In the present invention, as the resin used as the binder, any resin known in the paint field can be used, and examples thereof include polyester resins, polyolefin resins, polyamide resins, fluorine resins, silicone resins, and epoxy resins. . Of these, polyester resins or modified polyester resins (epoxy-modified polyester resins, thermosetting polyester resins such as polyester resins having a phenol derivative introduced into the skeleton, or unsaturated polyester resins) are preferable. is there.

  The melamine cross-linked polyester resin used for enhancing light resistance or the isocyanate (or block isocyanate) cross-linked polyester resin used for improving processability may be used separately from the binder resin. Is also used as a binder resin.

  Examples of white pigments include titanium oxide, zinc oxide, barium sulfate, and calcium carbonate. Among these, titanium oxide is particularly preferable for improving light resistance and reflectance, and both anatase and rutile types can be used. is there. Of these, rutile type titanium oxide is particularly preferable from the viewpoint of light resistance. The particle size is preferably about 0.1 to 1 μm. In order to improve the dispersibility in the resin, titanium oxide surface-treated with alumina, silica, zirconia or the like can also be preferably used. The blending amount of the white pigment with respect to the binder resin is 100% by mass when the total of the two (the total including the melamine cross-linked polyester resin or isocyanate or blocked isocyanate cross-linked polyester resin) is 100% by mass. It is good to make it into the range of 30-70 mass%. If the amount is too small, the reflectance will be low, and if it is too large, the mechanical strength of the coating film may be lowered.

  As the fluorescent substance, any substance that can absorb light in the ultraviolet region (less than 400 nm) and emit as visible light (400 nm or more) can be used. For example, 2,5-bis [5-t-butylbenzoxazolyl (2)] thiophene is commercially available under the trade name “UVITEX OB” (maximum absorption wavelength 375 nm; maximum emission wavelength 435 nm) manufactured by Ciba Specialty Chemicals. Other fluorescent substances are available under the trade name “Nikka Flow SC200” manufactured by Nippon Chemical Industry Co., Ltd. and the product name “Kayalite K” manufactured by Nippon Kayaku Co., Ltd.

  The amount of the fluorescent substance in the layer containing the fluorescent substance is preferably 0.1 to 15% in the layer. This is because, if the amount is too small or too large, the effect of improving the reflectance is hardly exhibited. The lower limit is more preferably 0.4%, still more preferably 0.8%. Further, the upper limit is more preferably 10%, still more preferably 8%.

  In order to form a light-reflective coating on a metal plate, a coating-forming coating containing a binder resin and a white pigment (fluorescent material, or a layer containing a melamine crosslinked polyester resin or an isocyanate crosslinked resin is formed. In some cases, they are further included) and a known coating method, that is, a roll coater method, a spray method, a curtain flow coater method, a bar coat method, a dipping method, or the like is used to form at least two layers on the metal plate surface Just apply. When the paint for forming a coating film contains a solvent, or when the binder resin is of a type that is thermally crosslinked, it is preferable to heat after coating. Additives known in the paint field such as pigments other than titanium oxide, UV absorbers, UV stabilizers, etc. may be added to the coating film-forming coating material as long as the object of the present invention is not impaired.

  As the metal plate, a steel plate or various metal plates can be used, and plating treatment, various known ground treatments, or the like may be performed. Moreover, well-known protective films, such as a clear coating film, may be formed on the light reflective coating film.

  When the reflective coated metal plate of the present invention is used as a reflective plate of a liquid crystal display device, a heat dissipating coating film is provided on the side opposite to the surface on which the reflecting coating film is formed, thereby imparting heat dissipation. Is desirable. As the heat-dissipating coating film, a black additive (carbon black, Fe, Co, etc.) having a particle size of 5 to 100 nm is added to the binder resin as described above (preferably, a combination of a modified polyester resin and a crosslinking agent). A coating film having a thickness of about 3 to 30 μm added with ˜15 mass% (amount in the coating film) is preferred. Moreover, when electroconductivity is calculated | required by a coating film, it is good to contain 10-50 mass% (content in a coating film) of electroconductive fillers (Ni, Ag, Zn, Fe, etc.). The heat-radiating coating film is described in detail in Japanese Patent Application Laid-Open No. 2004-74412 previously disclosed by the present applicant, and the reflective coated metal plate on which the heat-radiating coating film described in this publication is formed is Are all encompassed by the present invention.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. It is also possible to implement, and they are all included in the technical scope of the present invention.

Experimental example 1
(No. 1-19)
After applying a light-reflective coating to a 0.8 mm thick electrogalvanized steel sheet with a bar coater so that the coating thickness of each layer is 20 μm or 25 μm, the ultimate plate temperature is 220 ° C. in a baking furnace. A light-reflective coating film was formed by baking for 120 seconds. Table 1 shows the laminated structure of the coating film.

  As a binder resin constituting each layer of the coating film, 100 parts by mass of a polyester resin (trade name “Byron 29XS” manufactured by Toyobo Co., Ltd.) and a melamine resin (trade name “Sumimar M-40ST” manufactured by Sumitomo Chemical Co., Ltd.) 20 parts by mass of M) or 20 parts by mass of blocked isocyanate (trade name “Coronate 2507” manufactured by Nippon Polyurethane Co., Ltd.) (symbol I) is used, and the white pigment is titanium oxide (Taika) 50% by mass of a trade name “JR-603” manufactured by Kobayashi Co., Ltd., having an average particle size of 0.28 μm) was added. In addition, as a fluorescent substance, a trade name “UVITEX OB” (symbol O) manufactured by Ciba Specialty Chemicals, a trade name “Nikka Flow SC200” (symbol S) manufactured by Nippon Chemical Industry Co., Ltd., or a product name “manufactured by Nippon Kayaku Co., Ltd.” 1% by mass or 2% by mass of “Kayalite K” (symbol K) was added.

  In this experimental example, the light reflective coating film is counted as the first layer, the second layer, the third layer, and the fourth layer as viewed from the steel plate side. And in the four-layer type shown in Table 1, a layer not containing the fluorescent substance is formed on the upper layer side of the layer containing the fluorescent substance, and the layer containing the fluorescent substance or more than that Examples in which a polyester resin having a melamine cross-linked structure is contained on the upper layer side are examples, and those in which a fluorescent substance is contained or a polyester resin having a melamine cross-linked structure is not contained on the upper layer side. It is a comparative example.

  Table 2 shows the results of the light resistance test performed on each light-reflective coated metal plate. In Table 2, “after light resistance test” refers to the total reflectance after a 500 hour light resistance acceleration test using a xenon weather meter at a black panel temperature of 63 ° C. and no rain. .

  In Tables 1 and 2, no. Nos. 1, 2, and 3 are examples in which the coating layer having melamine crosslinking is present on the upper layer side of the layer containing a fluorescent substance. Compared to Comparative Examples 4, 5, and 6, the light resistance retention is high and the amount of decrease is small. No. 4 is an example having a melamine cross-link in a coating layer containing a fluorescent substance, and also has a light resistance superior to that in which no melamine cross-link is introduced into the layer or the layer above it. Has been obtained. No. No. 4 than No. 4. Since the light resistance of 1-3 is more excellent, it can be seen that it is more effective to provide the coating layer having melamine crosslinking on the upper side of the coating layer containing a fluorescent substance.

  No. Nos. 8 and 9 are examples in which a coating layer having melamine crosslinking was formed on the upper layer side of the layer containing a fluorescent substance. Compared to the comparative examples of 10, 11 and 12, it has much better light resistance. In these examples, the comparative example has a higher initial reflectance than the examples. However, in the comparative example, the reflectance is greatly reduced by the light resistance test, so the long-term stability of the quality and the product From the viewpoint of life, it can be said that the example is clearly superior.

  No. Examples Nos. 13, 14, and 15 Nos. 16 and 17 and No. 18 and No. 18 Similarly, it can be confirmed from 19 comparative examples that the light resistance is greatly improved by providing a coating layer having melamine crosslinking on the upper layer side of the coating layer containing a fluorescent substance.

Experimental example 2
The light-reflective coating metal plate No. 1 in Experimental Example 1 above. A heat-dissipating coating film was formed on the back surface of 1 (the opposite side of the light-reflecting coating film surface). The heat-dissipating coating film was composed of 50% by mass of the polyester resin, 10% by mass of the melamine resin, 10% by mass of carbon black (“MA100”; manufactured by Mitsubishi Chemical Corporation) as a black additive, and Ni powder (“ HCA-1 "; manufactured by Yamaishi Metal Co., Ltd .;) 30% by mass, and the thickness is 9 μm.

Evaluation of heat dissipation was performed by infrared integrated emissivity and heat dissipation. The infrared integrated emissivity was measured by the following method.
Apparatus: “JIR-5500 type Fourier transform infrared spectrophotometer” manufactured by JEOL Ltd.
And radiation measurement unit "IRR-200"
Measurement wavelength range: 4.5 to 15.4 μm
Measurement temperature: The heating temperature of the sample is set to 100 ° C. Integration count: 200 times Resolution: 16 cm ⁻¹

  Using the above apparatus, the spectral radiant intensity (measured value) of the sample in the infrared wavelength region (4.5 to 15.4 μm) was measured. Since the measured value of the above sample is measured as a numerical value with background radiation intensity and instrument function added / added, the emissivity measurement program [JEOL Co., Ltd. emissivity measurement program] Was used to calculate the integral emissivity. Details of the calculation method are as follows.

Where
ε (λ): Spectral emissivity of sample at wavelength λ (%)
E (T): Integrated emissivity (%) of sample at temperature T (° C.)
M (λ, T): Spectral radiant intensity of sample at wavelength λ and temperature T (° C)
(Actual value)
A (λ): Instrument function KFB (λ): Fixed background at wavelength λ (depending on sample
Spectral radiant intensity of unchanging background KTB (λ, TTB): of trapped black body at wavelength λ and temperature TTB (° C.)
Spectral radiant intensity KB (λ, T): Spectral radiant intensity of black body at wavelength λ and temperature T (° C)
(Calculated value from Planck's theoretical formula)
λ ₁ , λ ₂ : means the range of wavelengths to be integrated.

  Here, A (λ: instrument function) and KFB (λ: spectral radiant intensity of fixed background) are the measured values of the spectral radiant intensity of two blackbody furnaces (80 ° C., 160 ° C.), and Based on the spectral radiant intensity of black bodies in the temperature range (calculated value from Planck's theoretical formula), the following formula is used.

Where
M160 ° C. (λ, 160 ° C.):
Spectral radiant intensity of 160 ° C blackbody furnace at wavelength λ (actual measurement)
M80 ° C. (λ, 80 ° C.):
Spectral radiation intensity of 80 ° C blackbody furnace at wavelength λ (actual measurement)
K160 ° C (λ, 160 ° C):
Spectral radiation intensity of 160 ° C blackbody furnace at wavelength λ
(Calculated value from Planck's theoretical formula)
K80 ° C (λ, 80 ° C):
Spectral radiant intensity of black body furnace at 80 ° C at wavelength λ
(Calculated value from Planck's theoretical formula)
Means each.

In calculating the integral emissivity E (T = 100 ° C.), KTB (λ, TTB) is taken into account because a water-cooled trap black body is arranged around the sample in measurement. is there. By installing the trap black body, variable background radiation (meaning background radiation that varies depending on the sample. Since the radiation from the periphery of the sample is reflected on the sample surface, the measured value of the spectral radiant intensity of the sample is Spectral radiation intensity (which appears as a numerical value with background radiation added) can be controlled low. The trap black body uses a pseudo black body with an emissivity of 0.96, and the KTB [(λ, TTB): spectral radiant intensity of the trap black body at a wavelength λ and a temperature TTB (° C.)] is: Calculate as follows.
KTB (λ, TTB) = 0.96 × KB (λ, TTB)
In the formula, KB (λ, TTB) means the spectral radiant intensity of a black body at a wavelength λ and a temperature TTB (° C.).

  As for the infrared emissivity of the light-reflective coated metal plate on which the heat-radiating coating film was formed, the surface (light-reflecting coating film side) was 0.85 and the back surface (heat-radiating coating film side) was 0.86. Moreover, when the heat-radiating coating film was not attached, the emissivity on the back surface was 0.04.

On the other hand, the evaluation of heat dissipation (ΔT) was performed with the heat dissipation evaluation apparatus shown in FIG. FIG. 1 is a side sectional view of a rectangular parallelepiped device having an internal space of 100 mm (length) × 130 mm (width) × 100 mm (height). In FIG. 1, 1 is a test material (subject, measurement area is 100 × 130 mm), 2 is a heat insulating material, 3 is a heating element [the bottom area is 1300 mm ² , and the length of the longest straight line that can be drawn within the heating element area. (In FIG. 1, the length of the diagonal line is 164 mm), 5 is a temperature measuring device. As the heating element 3, a silicon rubber heater is used, and an aluminum plate (infrared emissivity is 0.1 or less) is used on the silicon rubber heater. In addition, a thermocouple is fixed as the temperature measuring device 5 at a position T1 in FIG. 1 [central portion of the internal space (above 50 mm from the heating element 3)]. In order to eliminate the influence of heat radiation from the heating element, the lower part of the thermocouple is covered. The heat insulating material 2 is a metal plate [for example, an electrogalvanized steel sheet (JIS SECC, etc.)] having an infrared emissivity of 0.03 to 0.06, and an ambient temperature (absolute temperature) at the T1 position is about 73 to The affixing method of the heat insulating material 2 is adjusted in advance so as to be in the range of 74 ° C. The heat dissipation was measured in a room at a temperature of 23 ° C. and a relative humidity of 60% in order to eliminate the influence of the outside air temperature.

  In the apparatus shown in FIG. 1, the heat-dissipating light-reflective coating metal plate is installed so that the light-reflective coating surface faces the heating element 3 (considering the lamp position as a heat source in the liquid crystal display device), and the power supply is turned on. Then, the heating element 3 is heated to 140 ° C. After confirming that the temperature of the heating element 3 is stably 140 ° C. and the temperature at the T1 position is 60 ° C. or higher, the light-reflective coating metal plate is once removed. When the temperature in the box drops to 50 ° C., the light-reflective coating metal plate is installed again, and the temperature in the box 90 minutes after the installation is measured. ΔT was measured five times for each test material, and the average value of three points of data excluding the upper and lower limits was defined as ΔT in the present invention.

  In this experiment, the temperature when using the light-reflective coating metal plate provided with the heat-radiating coating film and the light-reflective coating metal plate No. 1 having no heat-radiating coating film. When the difference in temperature (ΔT) when 1 was used was calculated, the heat dissipation ΔT of the light-reflective coating metal plate on which the heat dissipation coating was formed was 1.9 ° C.

  In addition, heat dissipation (DELTA) T with the temperature when the said light reflective coating metal plate to which the said heat-radiation coating film was provided and the electrogalvanized steel plate itself was used was 3.9 degreeC.

  The light-reflective coated metal plate of the present invention is easy to process, has excellent heat resistance and durability, and exhibits a high reflectance stably over the long term. For example, the reflection of an edge light type or direct type liquid crystal panel Useful for boards.

It is side part sectional drawing of a heat dissipation measuring apparatus.

Explanation of symbols

1 Test material (subject)
2 Heat insulation material 3 Heating element 5 Temperature measuring device

Claims (6)

A light-reflecting coated metal plate having a light-reflecting coating film having a structure in which a plurality of light-reflecting layers containing a white pigment and a binder resin are laminated , wherein at least one layer of the light-reflecting layer contains a fluorescent substance. a layer containing, and, at least the outermost layer of the light reflective coating contains a polyester resin having a melamine crosslinking, light, wherein the fluorescent material is higher thickness 5μm of the layer containing no Reflective painted metal plate.   The light-reflecting coated metal plate according to claim 1, wherein the thickness of the outermost layer in the light-reflecting coating film is 5 to 50 µm. The light-reflective coated metal plate according to claim 1 or 2, wherein at least one of the layers containing a fluorescent substance contains a polyester resin having melamine crosslinking .   The light reflective coated metal plate according to any one of claims 1 to 3, wherein the white pigment is titanium oxide.   The light-reflective coating metal plate in any one of Claims 1-4 in which the heat radiation coating film is formed in the other side of the surface in which the light-reflection coating film is formed. The light-reflective coating according to any one of claims 1 to 5, wherein a layer containing a polyester resin using isocyanate or blocked isocyanate as a crosslinking agent is formed on a lower layer side of a layer containing a polyester resin having melamine crosslinking. Metal plate.

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